Dennis Tedlock discusses the reliability of the text of the popol Voh; notes that, in spite of some debates, the bulk of the book has a "clean bill of health."
Dennis Tedlock, “Creation in the Popol Vuh: A Hermeneutical Approach,” in Symbol and Meaning Beyond the Closed Community: Essays in Mesoamerican Ideas, ed. Gary H. Gossen (Studies on Culture and Society 1; New York: Institute for Mesoamerican Studies, 1986), 77
Generations, including such figures as Brinton and Morley, have held the Popol Vuh to be the most important single native-language text in all the New World, and much emphasis has been laid on the pre-Columbian character of its contents. But the Popol Voh also has contents that reflect the fact that it was written after the Conquest, contents that have long been a source of embarrassment for Americanists. Bandelier wrote a century ago that the Popol Vuh “appears to be, for the first chapters, an evident fabrication, or at least an accommodation of Indian mythology to Christian notions—a pious fraud. But the bulk is an equally evident collection of original traditions of the Indians of Guatemala” (Bandelier 1878:391). More recently, Edmonson called the Popol Voh’s opening creation story a “syncretistic paraphrase of Genesis” (1967:359), again leaving the bulk of the book with a clean bill of health. Both these scholars make an issue of aboriginality, one of them recognizing that positive quality in all but the opening section and the other calling the opening a “paraphrase” of a nonindigenous book. What Bandelier called a “pious fraud” is given by Edmonson the more subtle term “syncretism,” but even syncretism carries negative connotations that go all the way back into Old World antiquity and were very much alive when anthropologists borrowed the term from modern historians of religion.